The present invention relates to materials for making a plasma display device and method of making the same, and, more particularly, to materials for making a plasma display in which the back panel is made of a metal core having layers of a dielectric material thereon and metal electrodes on and between the dielectric layers.
A typical plasma display includes a front panel and a back panel both made of sheet glass (e.g. conventional float-glass). Electrical connections and mechanical structures are formed on one of both of the panels. For example, the back panel may have a ribbed structure formed on it such that the space between the ribs defines a pixel in a direct current (DC) display or column of pixels in an alternating current (AC) display. The ribs prevent optical cross-talk, that is to say, plasma from one pixel leaking into an adjacent pixel. Fabrication of these ribbed structures, called barrier ribs, poses a challenge both in the materials and manufacturing techniques that are used.
Plasma displays operate by selectively exciting an array of glow discharges in a confined rarefied noble gas. Full color displays are made by generating a glow discharge in a mixture of gases, such as Hexe2x80x94Xe or Nexe2x80x94Xe gas mixture to produce ultraviolet light. The ultraviolet light excites phosphors in the pixel cell, as defined by the barrier ribs, to produce light of desired color at the pixel position.
A typical plasma display back panel comprises a glass substrate having a plurality of substantially parallel, spaced first electrodes on a surface thereof. In AC displays, a thin layer of a dielectric material, such as a glass, covers the electrodes. Barrier ribs are formed on the surface of the glass substrate between the first electrodes. The barrier ribs project from the surface of the substrate at a distance greater than the thickness of the first electrodes. Red, green and blue (R-G-B) phosphor layers overlie alternating columns of the first electrodes in the spaces between the barriers and also overlie the walls of the barriers. A front transparent glass substrate, the front panel, overlies the rear panel and may rest on the barrier ribs so as to be spaced from the rear glass substrate by the barrier ribs.
Typically, the barrier ribs are walls which define troughs or channels on the back panel. Alternating current (AC) plasma displays typically have barriers that form the separators for the column pixels, and hence, have continuous vertical ribs on the back plate. By contrast, direct current (DC) plasma displays typically have ribbed barriers which isolate each pixel from all of its neighbors. Thus, for DC displays, the rib structure has a rectangular lattice-like layout. In either case, the desired resolution for the display device and its size determine the size of the ribbed barriers. In a typical display, the ribs are 0.1 to 0.2 mm in height, 0.03 to 0.2 mm wide and on a 0.1 to 1.0 mm pitch.
The barriers may be formed on the back plate by laminating a ceramic green tape to the back plate, sandblasting the green tape to form the channels between the barriers and then firing the back plate in a kiln to convert the green tape barriers into ceramic barriers, as set forth in U.S. Pat. No. 6,140,767, entitled xe2x80x9cPLAMSA DISPLAY HAVING SPECIFIC SUBSTRATE AND BARRIER RIBSxe2x80x9d to Sreeram et al.
The front panel includes an array of substantially parallel, spaced second electrodes on its inner surface. These second electrodes extend substantially orthogonally to the first electrodes. A layer of a dielectric material, typically glass, covers the second electrodes. A layer of MgO covers the dielectric layer. Voltages applied to the electrodes in the proper manner excite, maintain and extinguish a plasma in the gas within the region formed by the barriers. Addressing of individual pixels is done using external circuitry at the periphery of the panel. Barrier structures are typically used to confine the discharge to the addressed pixel, eliminating both electrical and optical cross talk between adjacent pixel elements. The columns of pixels are separated by the barriers, and the first electrodes are arranged beneath the gaps between the barriers. In a DC plasma display, the electrodes are not covered with glass or MgO, and the barrier structures are typically crossed, providing a box-like structure at each pixel element.
A composition of materials to fabricate high resolution, low-temperature cofired ceramic-on-metal plasma display back panels, comprising a metal substrate having a predetermined thermal coefficient of expansion and a glass material formulation bonded to the metal core, comprising at least two glasses such that the thermal coefficient of expansion of the formulation closely matches that of the metal substrate.
In an exemplary embodiment of the invention, the metal substrate is made of titanium.
In another exemplary embodiment of the invention, the glass material formulation is comprised of at least two glasses. The first glass material includes ZnO MgO, B2O3, and SiO2, and has a formulation, by percent weight, of:
and a second glass material has a formulation defined by weight percent as:
In yet another exemplary embodiment of the invention, the mixture of the first and second glass materials has a thermal coefficient of expansion (TCE) nearly equal to that of the titanium metal substrate. A glass mixture with a TCE nearly equal to that of the titanium metal substrate may have a formulation defined by percent weight as: